1. Field of the Invention
This invention relates to magnetic pickups for stringed musical instruments.
2. Prior Art
One-coil or two-coil magnetic pickups have been utilized for transducing the vibration of strings in musical instruments to corresponding electrical signals.
In a single-coil magnetic pickup, a coil wound around a permanent magnet core has electric currents induced therein when a string passing in proximity to the core vibrates. The vibration of the string varies the magnetic field through the core to induce a corresponding electric current. A separate permanent magnet is provided for each string, with the coil being common to all cores.
Single-coil pickups are susceptible to stray magnetic fields which cause hum or other noise. To eliminate the hum, an added coil has been serially connected out of phase. The stray fields generate equal and opposing currents which cancel each other. U.S. Pat. No. 2,896,491 to Lover describes the two-coil system in detail.
In either the one-coil or two-coil system, the pickup sensitivity for each string can be altered by providing ferromagnetic screws in the magnetic cores which are adjustable in order to adjust the height of the cores.
Prior pickups have low power output due to high flux path impedances. Therefore, substantial amplification of the pickup output is necessary. Prior designs also have a relatively low signal to noise ratio.
The prior magnetic pickups are also expensive to manufacture since individual polepieces or cores must be produced, assembled and adjusted for each string and each coil. Further, screw-type adjustments may be accidentally altered.